Keep track of whether mbedtls_ssl_set_hostname() has been called
Use a special marker as ssl->hostname if mbedtls_ssl_set_hostname() has been
called with NULL. If mbedtls_ssl_set_hostname() has never been called, the
field is NULL, as before.
No behavior change apart from now emitting a different log message depending
on whether mbedtls_ssl_set_hostname() has been called with NULL or not at all.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index a7bfd7b..566ec0e 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1892,6 +1892,10 @@
* If this is \p NULL, the peer name verification is skipped,
* the server_name extension is not sent, and the server name is ignored
* in TLS 1.3 session resumption using tickets.
+ *
+ * This can be a special value to indicate that mbedtls_ssl_set_hostname()
+ * has been called with \p NULL, as opposed to never having been called.
+ * See `mbedtls_ssl_get_hostname_pointer()` in `ssl_tls.c`.
*/
char *MBEDTLS_PRIVATE(hostname);
#endif /* MBEDTLS_X509_CRT_PARSE_C */
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index c3b7497..993c69e 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2758,6 +2758,12 @@
#if defined(MBEDTLS_X509_CRT_PARSE_C)
+/* A magic value for `ssl->hostname` indicating that
+ * mbedtls_ssl_set_hostname() has been called with `NULL`.
+ * If mbedtls_ssl_set_hostname() has never been called on `ssl`, then
+ * `ssl->hostname == NULL`. */
+static const char *const ssl_hostname_skip_cn_verification = "";
+
#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
/** Whether mbedtls_ssl_set_hostname() has been called.
*
@@ -2770,11 +2776,6 @@
static int mbedtls_ssl_has_set_hostname_been_called(
const mbedtls_ssl_context *ssl)
{
- /* We can't tell the difference between the case where
- * mbedtls_ssl_set_hostname() has not been called at all, and
- * the case where it was last called with NULL. For the time
- * being, we assume the latter, i.e. we behave as if there had
- * been an implicit call to mbedtls_ssl_set_hostname(ssl, NULL). */
return ssl->hostname != NULL;
}
#endif
@@ -2786,12 +2787,16 @@
#endif
const char *mbedtls_ssl_get_hostname_pointer(const mbedtls_ssl_context *ssl)
{
+ if (ssl->hostname == ssl_hostname_skip_cn_verification) {
+ return NULL;
+ }
return ssl->hostname;
}
static void mbedtls_ssl_free_hostname(mbedtls_ssl_context *ssl)
{
- if (ssl->hostname != NULL) {
+ if (ssl->hostname != NULL &&
+ ssl->hostname != ssl_hostname_skip_cn_verification) {
mbedtls_zeroize_and_free(ssl->hostname, strlen(ssl->hostname));
}
ssl->hostname = NULL;
@@ -2816,13 +2821,19 @@
* so we can free it safely */
mbedtls_ssl_free_hostname(ssl);
- /* Passing NULL as hostname shall clear the old one */
-
if (hostname == NULL) {
- ssl->hostname = NULL;
+ /* Passing NULL as hostname clears the old one, but leaves a
+ * special marker to indicate that mbedtls_ssl_set_hostname()
+ * has been called. */
+ /* ssl->hostname should be const, but isn't. We won't actually
+ * write to the buffer, so it's ok to cast away the const. */
+ ssl->hostname = (char *) ssl_hostname_skip_cn_verification;
} else {
ssl->hostname = mbedtls_calloc(1, hostname_len + 1);
if (ssl->hostname == NULL) {
+ /* mbedtls_ssl_set_hostname() has been called, but unsuccessfully.
+ * Leave ssl->hostname in the same state as if the function had
+ * not been called, i.e. a null pointer. */
return MBEDTLS_ERR_SSL_ALLOC_FAILED;
}
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 73d17f0..a88ff3b 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -6080,9 +6080,11 @@
run_test "Authentication: hostname match, client required" \
"$P_SRV" \
- "$P_CLI auth_mode=required server_name=localhost debug_level=1" \
+ "$P_CLI auth_mode=required server_name=localhost debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -C "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "! mbedtls_ssl_handshake returned" \
-C "X509 - Certificate verification failed"
@@ -6134,7 +6136,7 @@
run_test "Authentication: hostname mismatch, client optional" \
"$P_SRV" \
- "$P_CLI auth_mode=optional server_name=wrong-name debug_level=1" \
+ "$P_CLI auth_mode=optional server_name=wrong-name debug_level=2" \
0 \
-c "does not match with the expected CN" \
-c "x509_verify_cert() returned -" \
@@ -6142,93 +6144,115 @@
run_test "Authentication: hostname mismatch, client none" \
"$P_SRV" \
- "$P_CLI auth_mode=none server_name=wrong-name debug_level=1" \
+ "$P_CLI auth_mode=none server_name=wrong-name debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -C "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname null, client required" \
"$P_SRV" \
- "$P_CLI auth_mode=required set_hostname=NULL debug_level=1" \
+ "$P_CLI auth_mode=required set_hostname=NULL debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -c "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "! mbedtls_ssl_handshake returned" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname null, client optional" \
"$P_SRV" \
- "$P_CLI auth_mode=optional set_hostname=NULL debug_level=1" \
+ "$P_CLI auth_mode=optional set_hostname=NULL debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -c "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname null, client none" \
"$P_SRV" \
- "$P_CLI auth_mode=none set_hostname=NULL debug_level=1" \
+ "$P_CLI auth_mode=none set_hostname=NULL debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -C "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname unset, client required" \
"$P_SRV" \
- "$P_CLI auth_mode=required set_hostname=no debug_level=1" \
+ "$P_CLI auth_mode=required set_hostname=no debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -c "Certificate verification without having set hostname" \
+ -c "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "! mbedtls_ssl_handshake returned" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname unset, client optional" \
"$P_SRV" \
- "$P_CLI auth_mode=optional set_hostname=no debug_level=1" \
+ "$P_CLI auth_mode=optional set_hostname=no debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -c "Certificate verification without having set hostname" \
+ -c "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname unset, client none" \
"$P_SRV" \
- "$P_CLI auth_mode=none set_hostname=no debug_level=1" \
+ "$P_CLI auth_mode=none set_hostname=no debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -C "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname unset, client default, server picks cert, 1.2" \
"$P_SRV force_version=tls12 force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-128-CCM-8" \
- "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=1" \
+ "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -c "Certificate verification without having set hostname" \
+ -c "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
requires_config_enabled MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED
run_test "Authentication: hostname unset, client default, server picks cert, 1.3" \
"$P_SRV force_version=tls13 tls13_kex_modes=ephemeral" \
- "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=1" \
+ "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -c "Certificate verification without having set hostname" \
+ -c "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
run_test "Authentication: hostname unset, client default, server picks PSK, 1.2" \
"$P_SRV force_version=tls12 force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8 psk=73776f726466697368 psk_identity=foo" \
- "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=1" \
+ "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -C "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"
requires_config_enabled MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED
run_test "Authentication: hostname unset, client default, server picks PSK, 1.3" \
"$P_SRV force_version=tls13 tls13_kex_modes=psk psk=73776f726466697368 psk_identity=foo" \
- "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=1" \
+ "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
0 \
-C "does not match with the expected CN" \
+ -C "Certificate verification without having set hostname" \
+ -C "Certificate verification without CN verification" \
-C "x509_verify_cert() returned -" \
-C "X509 - Certificate verification failed"